Antiskid apparatus

ABSTRACT

Antiskid apparatus wherein the velocity of two axles is electrically measured and a signal representing the velocity difference is fed to a differentiator device which operates a switching circuit when the change in velocity difference exceeds a predetermined value. The switching circuit then operates an antiskid device to reduce the velocity difference. A time delay is coupled to the switching circuit to maintain the switching circuit operated for a predetermined period of time after the switching circuit input is turned off (that is, after the change in velocity difference falls below a predetermined value.

United States Patent 11 1 Softer et al. 51 Aug. 7, 1973 1 54] ANTISKIDAPPARATUS 3,574,415 4/1971 Stamm 303 21 EB 3,606,491 9 1971 Walsh'",188/1111 C l751 Inventors: Jacques Sceauz; Franm's 3,608,978 9/1971Neisch 303/21 EB Tonnerieux, Fontenay Aux Roses, both of France PrimaryExaminerRichard A. Schacher [73] Assignee: Societe Generale deConstruction A y yn & Ffishauf Electriques et Mechaniques (Alstom),Paris, France [57] ABSTRACT [22] Fil d; N 18, 1970 Antiskid apparatuswherein the velocity of two axles is electrically measured and a signalrepresenting the ve- [21 1 App! 90765 locity difference is fed to adifferentiator device which operates a switching circuit when the changein veloc- 52 U.S. c1. 303/21 EB, 188/181 c y difference exceeds apredetermined value- The 151 1 1m. (:1 B60t 8/06 switching eireuit thenOperates an amiskid device to [58] Field of Search 303/21 EB; du'ee thevelocity differenee- A time delay is p' I9 188/181 C; 317/5; 340/263 theswitching circuit to maintain the switching circuit operated for apredetermined period of time after the [56] References Ci d switchingcircuit input is turned off (that is, after the UNITED STATES PATENTSchange in velocity difference falls below a predeter- 3,503,654 3 1970Stamm 303 21 EB mmed l 3,556,610 1/1971 Leiber 303/21 P 4 Claims, 1Drawing Figure 1 v I, p (2 10a, I

J 1 VELOCITY VELOCITY DETECTOR DETECTOR VELOCITY DIFFERENCENZ) DETECTOR\DIFFERENTIATOR l 015v1c1:

MULTI- I VIBRATOR N 5 TIME 7 DELAY 5x10 CONTROLLER 6 ANTISKDD DEVICEPATENT E0 ms 1 ms VELOCITY DETECTOR I VELOCITY DETECTOR VELOCITYDIFFERENCE DETECTOR MULTI- VIBRATOR \DIFFEQENTIATOR DEVICE TIME DELAYSKI D CONTROLLER ANTISKID DEVICE 1 ANTISKID APPARATUS The presentinvention relates to antiskid apparatus, including a novel skid-detectordevice, intended to prevent the slipping or skidding of a wheel, andmore particularly to such a device which is particularly useful inmotorized railroad vehicles.

Antiskid devices are known wherein the slipping of wheels is detectedand is corrected. These devices generally compare the velocities of twoor more axles, or,

measure acceleration of an axle. In most of the known antiskid systems,the velocities or acceleration are converted into continuous electricalsignals, which are fed into a measurement device. In some other knownsys-;

SUMMARY OF THE INVENTION The antiskid apparatus of the present inventionincludes means for measuring the velocity difference between tworotating axles. A differentiator device is placed at the output of thevelocity difference measuring means. When the derivative exceeds apredetermined value a switching means responsive to the output of thedifferentiator device operates an antiskid device. A delay means iscoupled to the switching device for maintaining the antiskid deviceoperable for a predetermined period of time after the input signalthereto is turned off.

The present invention will be better understood from the followingdetailed description taken in conjunction with the accompanying singleFIGURE which schematically illustrates an embodiment of the presentinvention. a

Referring to the single FIGURE, the velocities of axles 9 and 10 aremeasured by velocity detectors 1 and 2, respectively, which generateoutput signals which are a function of the detected velocity. The outputsignals from detectors 1 and 2 are fed to a velocity difference detector3 which measures the velocity difference between the two axles. Velocitydifference detector 3 may be, for example, a comparator circuitproviding an output signal which is a function of the difference betweenthe input signals thereto. Such comparators are well known in the art,as are velocity detectors 1 and 2. The output signal of velocitydifference detector which may be termed a speed difference signal 3 isconnected to a differentiator circuit 4. A multivibrator 5 is coupled tothe output of differentiator circuit 4 which operates multivibrator 5when the value of the derivative signal exceeds a predeterminedthreshold value, or skid threshold." When the skid threshold" isexceeded, multivibrator 5 is operated and in turn operates a skidcontroller 6 which is coupled to the output thereof. Skid controller 6preferably is a switching circuit such as a relay, transistor switch, orthe like. When controller 6 is operated, it controls antiskid device 8,which is constructed in accordance with known principles. Antiskid dvice8 may be coupled to axles 9 and 10 and functions to reduce the rate ofchange of the velocity difference between axles 9 and 10. Such antiskiddevices are well known in the art and are therefore not discussed indetail herein.

A time delay device 7 is coupled between skid controller 6 andmultivibrator 5 to maintain the controller 6 operated for apredetermined period after multivibrator 5 is turned off. That is, theantiskid device 8 remains operative for a predetermined period of timeafter the derivative of the velocity difference between axles 9 and It)falls below a value corresponding to the skid threshold." I

The particular design of each of the individual ele-. ments shown in theattached FIGURE is conventional and should be apparent to those skilledin the art. For example, velocity detectors generating electrical output signals and differentiator circuits responsive to electrical signalsare well known. Skid controller 6 may, in a particular embodiment,comprise merely a relay. The time delay 7 may comprise a standard typeof time delay element which is instantly actuated and which remainsactuated for a predetermined period of time after its actuating signalis removed. Alternatively, the skid controller 6 and the time delayelement 7 can be combined into a single time delay relay which iscommercially available.

While the apparatus of the present invention is particularly useful inrailroad vehicle applications, it should be clear that the principles ofthe invention are equally applicable for use in other types of vehiclesor in any other application where the object is to detect and controlslipping or skidding of a wheel or axle. It should be clear that manymodifications and alterations may be made to the specific describedembodiment of the present invention .within the scope thereof as setforth in the accompanying claims.

We claim:

1. Antiskid apparatus comprising:

means (1, 2, 3) for measuring the velocity difference between tworotating axles (9, l0) and providing a speed difference signal;

a differentiator device (4) connected to the output from the velocitydifference measuring means (1-3) differentiating the speed difi'erencesignal and generating a derivative output signal;

switching means (5, 6) coupled to the output of said differentiatordevice (4) and operated when said derivative output signal exceeds apredetermined value;

an antiskid device (8) responsive to the output of said switching meansand being operable to reduce the rate of change of the velocitydifference between said two axles; and

delay means (7) coupled to said switching means (5,6) and holding saidantiskid device in operated condition to extend the operating time ofthe antiskid device beyond the time when the input signal to theswitching means has ceased maintaining said antiskid device (8)effective for a predetermined period of time after the input signal tosaid switching means is removed.

2. Apparatus according to claim 1 wherein said switching means includesa multivibrator (5) coupled to the output of said differentiator device,and a switching device (6) coupling the output of said multivibrator (5)to said antiskid device (8).

3 4' 3. Apparatus according to claim 2 wherein said switching device (6)operated for a predetermined'pesw'tchmg devce (6) a relay' riod of timeafter the inputsignal to said multivibrator 4. Apparatus according toclaim 2 wherein said delay means (7) is coupled between saidmultivibrator and said switching device (6) for maintaining said 5 isturned off.

1. Antiskid apparatus comprising: means (1, 2, 3) for measuring thevelocity difference between two rotating axles (9, 10) and providing aspeed difference signal; a differentiator device (4) connected to theoutput from the velocity difference measuring means (1-3)differentiating the speed difference signal and generating a derivativeoutput signal; switching means (5, 6) coupled to the output of saiddifferentiator device (4) and operated when said derivative outputsignal exceeds a predetermined value; an antiskid device (8) responsiveto the output of said switching means and being operable to reduce therate of change of the velocity difference between said two axles; anddelay means (7) coupled to said switching means (5,6) and holding saidantiskid device in operated condition to extend the operating time ofthe antiskid device beyond the time when the input signal to theswitching means has ceased maintaining said antiskid device (8)effective for a predetermined period of time after the input signal tosaid switching means is removed.
 2. Apparatus according to claim 1wherein said switching means includes a multivibrator (5) coupled to theoutput of said differentiator device, and a switching device (6)coupling the output of said multivibrator (5) to said antiskid device(8).
 3. Apparatus according to claim 2 wherein said switching device (6)is a relay.
 4. Apparatus according to claim 2 wherein said delay means(7) is coupled between said multivibrator (5) and said switching device(6) for maintaining saiD switching device (6) operated for apredetermined period of time after the input signal to saidmultivibrator is turned off.